The invention relates to gas turbine engines, and more particularly to rotors for gas turbine engines.
Gas turbine engines operate according to a continuous-flow, Brayton cycle. A compressor section pressurizes an ambient air stream, fuel is added and the mixture is burned in a central combustor section. The combustion products expand through a turbine section where bladed rotors convert thermal energy from the combustion products into mechanical energy for rotating one or more centrally mounted shafts. The shafts, in turn, drive the forward compressor section, thus continuing the cycle. Gas turbine engines are compact and powerful power plants, making them suitable for powering aircraft, heavy equipment, ships and electrical power generators. In power generating applications, the combustion products can also drive a separate power turbine attached to an electrical generator.
Gas turbine engines require substantial amounts of high pressure oil to lubricate the rotor bearings. During some transient operations, and in particular during start-up, clearances exist which permit leakage of the oil into the interior of the rotor assembly. If the oil remains trapped within the rotor, rotor unbalance and the increased potential for fire can result. Rotor unbalance has been shown to lead to destructive vibration, which significantly reduces the serviceable life of the rotor.
In some gas turbine engines, a hub connects a forward disk to a shaft. The hub and disk are highly loaded with dynamic torque and radial and axial loads. To avoid rotor unbalance, some provision for drainage of leakage oil from the hub and disk must be made or the oil will become trapped. Prior designs have placed small drainage holes through the hub and/or disk. However, the use of these holes in the highly stressed hub and disk creates stress concentrations and decreases the low cycle fatigue life of these parts.